Conventional administration of vaccine or other injectable drugs via a reusable syringe is a perfectly adequate and an economic approach where the administration is done by professional staff and in facilities where the circulation of the syringe can be managed and controlled. The syringe can then be sterilized for reuse, refilled and administered by trained, skilled professional personnel.
There are, however, situations where injections are given to large numbers of individuals over a short period of time and where it is virtually impossible to sterilize equipment and further, the administration of the drug or vaccine will be done by non-professional but trained personnel. Because of cost, these situations typically preclude use of a standard disposable syringe. It is known that for these circumstances, a single dose prefilled vaccine delivery system has been developed wherein the single dosage syringe has a squeezable body portion permitting the rapid administration of the dose.
Prior art devices which deal with the area of disposable syringes include U.S. Pat. No. 2,618,263 granted to Lakso Nov. 18, 1952 discloses a single use syringe wherein the needle and the medicant containing portion are encapsulated in a rigid envelope, the top portion being broken off to expose the injection needle and the bottom portion includes a window-like portion such that the bladder may be compressed and the medicant expressed.
U.S. Pat. No. 4,013,073 granted to Cunningham on Mar. 22, 1977 discloses a dispensing device wherein the medicant containing syringe portion includes an internally facing interacting interlock system that when the walls of the bladder portion are squeezed the inner surfaces interlock preventing reuse.
U.S. Pat. No. 4,022,206 granted to Hilleman et al on May 10, 1977 discloses a vaccine delivery system including single dosage syringes having a squeezable body portion and a separate package containing water to reconstitute lyophilized vaccine.
U.S. Pat. No. 4,391,273 granted to Chiquiararias on July 5, 1983 discloses a non-reusable disposable syringe wherein the use of the piston effectively destroys the syringe.
U.S. Pat. No. 4,548,601 granted to Lary on Oct. 22, 1985 discloses a pharmaceutical and hypodermic needle combination including a semi-rigid outer container surrounding a substantially nonresilient inner container which contains the premeasured dose of the pharmaceutical. When administered the interior envelope collapses and remains in the collapsed condition.
The reuse of the prior art devices which are not self-destructing presents a problem in that the device is no longer sterile and, therefore, the risk of infection is great. Further, often times the reuse typically occurs in settings outside the formal health care system. The rapid spread of acquired immune deficiency syndrome among intravenous drug users has occurred in part due to this reuse.
Those prior art devices which are not capable of reuse are expensive to manufacture and/or are bulky and thus inconvenient to ship and store.
In addition, most of the devices fail to provide the capability for performing aspiration to determine proper placement of the needle. In performing an injection, medical practitioners are trained to "aspirate" before injecting in order to confirm whether the needle is or is not in a blood vessel. Aspiration is accomplished by drawing a negative or suction pressure and visually examining for blood that is transferred into the medicant solution through the needle. In the administration of an intravenous injection the presence of blood indicates proper placement. In the administration of an intramuscular injection, the presence of blood indicates improper placement. Aspiration is not possible at any time in the use of many of the prefilled devices as the contents of the receptacle are under a positive pressure to express the medicant.
The functional requirements for a product that allows aspiration as well as a means for providing a positive internal pressure to prevent subsequent refilling have conflicted in prior art devices.